Heat treating fluid coke compactions



Jan. 8, 1957 c. E. JAHNIG ET A HEAT TREATING FLUID COKE COMPACTIONSFiled June 29, 1955 -HEATER WET -COMPfifiTIONS I I I DRIED COMPACTIONSOUT FIG-2 S y r w W n n e r m m A m g i n mmm M U0 WWM HA2 may 4! mmm wCWH United States Patent Q i \JI'IEAT. TREATING FLUID COKE COR/[PACTIONSCharles E." Iahnig, 'Rnmson, and Walter-A. Worth and HomerZ. Martin;'Cranford,"N. .Lyassignors to' Esso T Research J and EngineeringGompany; a corporation of 1 Delaware Applicationlune29, 1955,..SerialNo.518,865

' t 6' Claims. c1. 202-14 This invention relates to improvements in theheat hardeningoflfluid coke'compactions. More particularly it relates'toa process of this nature wherein the compactions are heat hardened bytreating'them while in the form of amoving bedcountercurrent to"fluidized coke particles. It also. relates to a process wherein thistreatment is carried out in a pluralityof. superposed beds.

1 There has recently been developed an improved process known asthefluid coking process'for the production of fluidcokeand the thermalconversion of heavy hydrocarbon -oils to. lighter fractions, e. g., seeSerial No. 375,088 filed August 10,1953. For completeness the process isdescribed in further detail below although it should be understoodthatthe fluid coking process itself is no part of this invention.

.IThe'Iflu'id coking unit consists basically of a reaction vessel orcoker and a. heater or burner vessel. In a typical .operation the heavyoil"tobe processed is injected into .the reaction. vessel containing adense, turbulent, fluidized bed. of hot inert solid particles,preferably coke particles. A transfer line or staged. reactors canbeemlployed. Uniform temperature. exists in the coking bed. Uniformmixingin the bed results in virtually isothermal .conditions and.'eifects.instantaneous distribution of the feed stock.) In the reactionzone the feedstock is partially vaporized and partially cracked.[Product vapors areremoved. from the coking vessel and sent toafracti'onator forthe recovery of gas and light distillatestherefrom.Any..heavy bottomsis usually returned to the coking vessel. Thecoke-produced in the process remains in the bed coated on the solidparticles. Stripping steam is injected into the stripper to removeoil'from'the coke particles prior to the passage of the coke'tothe-burner.

The heat for carrying out the endothermic cokingreaction is generated inthe'burner'vessel, usually'but not necessarily separate. A stream ofcoke'isthus transferred from the reactor-.toatheburner vesselgisuch' asa transfer line-or fluid bed. burner, employing a standpipe and n'sersystem; air being supplied to the riser for conveying the solids totheburner. Sufficient coke or added carbonaceous matter is burned in theburning-vessel-to bringthe solids therein up to a temperaturesuificient'tozmaintain .the, system in. heat balance. The burnersolidsaremaintained at a higher temperature than theisolidsinthezreactor. About 5% -of-coke,- based on the feed, is .burnedfor thispurpose. This may amount to approximately 15% to of-the coke made in theprocess. Thenet coke production, which'represents the coke make less thecoke burned, is withdrawn.

. Heavy hydrocarbon oil feeds suitable for thecoking process includeheavy crudes, atmospheric and crude vacuum bottoms, pitch, asphalt,other heavy. hydrocarbon petroleum residua or mixtures thereof..Typically such =feeds can have an initial boiling point of about 700 F.or ..higher,.an-A. P. I. gravity of about 0 to 20, .and aConradsoncarbon residue content of about 5 to 40 wt. percent. (As to Conradsoncarbon residuesee .A.; S. T'.-M. Test D-1-89-41.)

A- problemin the marketing of. the fluid coke product is thesm'allsizeofthe particles,'predon1inantly, i. e., about "6090 wt. percenhin'the'range of 20 to mesh. The production of substantially larger particles isinconsistent with satisfactory operation of the fluid bed. On the otherhandindustrial requirements for coke often necessitate particles havingadiameter of about at least A; inch to 1 inch..

Compactions of theindicated size made from fluid coke are of severaltypes, i. e., pellets, extrusions, and briquettes. All have in commonthe. utilization of an agglutinating carbonaceous substance as a binder.

The agglutinating carbonaceous binder s'ubstances'that can be utilizedinclude suitablehydrocarbon binders, .such as asphalt and other heavypetroleum residues, aromatic tars, .e... g. vacuumreduced thennal tars,heavy ends of coal tar, such as coal tar pitches having a minimum s0ft-'ening point of about 100 C., and heavy ends from the coking operation,i. e., 1050 F.+ material. Some specific trade. examples of the bindersare Elk Basin residuum (160 F. softening point) ,Enjay 160 Asphalt andHawkins coker' bottoms. These substances are utilized in an amount ofabout 5 to 20 wt. percent based on the coke charge and preferably 8 to15 wt. percent.

"The fluid coke can be used as is to make briquettes, but the behaviorofbriquettes during heating and the strengthv ofthe final products areimproved by grinding part or all of the coketo produce finer particles.

If the coke is to be pelletized by tumbling, it must be' ground. Pelletsin general are prepared by grinding the: fluid coke tofgive a'fines'fr-action, e. g., minus 100 mesh, and mixing the coke with about10%. binder by tumbling. The binder is groundeither separately or inmixtures with the coke. Enjay 160 asphalt can be ground by itself. Elk,Basin and Hawkins coker-bottoms may become too sticky, evenwhen mixedwith coke,.to.enable grinding at normal temperatures. I Consequently,artificial cooling. may beused to. grind mixtures of these asphalts andcoke. These mixtures (about %..to coke and 10% vto 15% asphalt)..areground in. a, ball or other mill with about 25%. water or similarliquid.Artificial cooling may .beused to hold thetemperature below 75 F. Theground mixture. isfilteredand the product containing about 25 water. ispassedlthrougha screento break upthelumps- Thesepellets are then chargedto a rotating drum for ballingsoas to subject them to a rolling motionon a -horizontallyrot-ated surface.

. The briquettes are-prepared by. admixture of the'fluid'. coke as is orpartially ground with about 10%-of -an agglutina-ting.carbonaceoussubstance at atemperature of about '200 to 300 -1 Themixture is .briquetted in a hydraulic press at a pressure oft aboutQlOOto-9600 p. s. i. I Roll presses tsuch-as=those commonly employedzto makebriquettes fronrcoal and other'materials can be used. Such machines. aredescribed in .the 'Chemicalj Engineering articleAgglomerat-ion,..October 1951. .The machines :areitequippedwith steamheated-t mixers when=briquettes are made-with tar binders. The hotmixtures pas-s directly to the pressing rolls.

Allthese compactions require heat hardening at temtperatures of above7Q0"*F:- to -decompose the binder to a' carbonaceous'res'idue and toproduce adequate strength and cohesion. Treating atthese temperatures,however, because of-the' melting of the binder material results in thedeformation of the comp-actions and also adherence to eachother. Inaddition of' course elevated temperatures tend to oxidize thecompactions undesirably.

This invention provides .an'improved method of thermally hardening thecompactions of fluid coke which overcomes thesedifiic'ulties. The methodcomprises'contacting 'the compactionsvi hile inthe form .of a movingbed, countercurrently to fluidized coke particles at heat treatingtemperatures. In a preferred modification the heat treatment is carriedout in a plurality of superposed zones in which the compactions are inthe form of shallow moving beds contained in dense, turbulent, fluidizedbeds of coke particles. The coke particles utilized for the heattreating are preferably fluid coke particles and the size distributioncan be substantially the same as the fluid coke obtained from the fluidcoking process without grind- The heat hardening temperature utilized isin the range of 700 F. or higher, preferably 1000" to 1800 F. The timeis for about 15 minutes to 2 hours.

Counter-current heating provides:

1. Slow evolution of the vapors so the briquettes are not exploded orcracked.

2. Products from cracking binder are not so severely cracked (e. g. lesslow value gas).

3. Better heat economy on the heater.

4. Lower circulation rate required on hot solids.

The eflicacy of this very specific method of heat treating thecompactions is surprising in that other heat treating methods givedistinctly inferior results. Thus more than substituting one method ofheat treating for another is involved. The reducing atmosphere presentin the fluidized coke particles maintained at this temperature alsocontributes to the desired results.

This invention will be better understood by reference to the followingexamples and descriptions in connection with the flow diagrams shown inthe drawings.

Figure l is a flow diagram of the heat treating of the compactions in asingle, dense, turbulent, fluidized bed.

Figure 2 is a flow diagram of an alternative modification utilizing aplurality of superposed beds.

Referring now to Figure l briquettes prepared from fluid coke and 10 wt.percent Elk Basin residuum binder by molding at a pressure of about 9000p. s. i. and at a temperature of 275 F. are fed through line 1 into anupper portion of elongated vertical heat treating vessel 2. Thecompactions fall countercurrently through a dense, turbulent, fluidizedbed of fluid coke 3 at a temperature of 1200 F. having an upper level 4.The compactions are thus heat treated for 30 minutes. The compactionsform a moving bed with more packing at a lower portion 5 of the heattreating vessel where there is no longer any problem of adhesion ordeformation.

Fluidizing gas such as steam, light hydrocarbon, or inert gas is addedthrough line 6 to give a superficial velocity of .1 to 3 ft./sec., e. g..5 ft./ sec. This is sulficient to fluidize the coke particles but notthe compactions. The fluidizing gas may be admitted in two portions vialines 6:: and 6b so as to secure some aeration of the compactions. Aportion of the fluid coke is withdrawn from an upper portion of thevessel through line 7 and sent to a separate heating vessel 8 where itis heated to a temperature in the range of 1000 to 1800 F., e. g. 1500F. 'Ihis heating can be done by combustion with air, heat exchange withan inert material such as shot, in a fluid bed heater, a transfer lineheater or other means known in the art. The reheated solids are returnedto a lower portion of vessel 2 through line 9. Countercurrent contactwith the compactions is thereby obtained. The heat hardened compactionsare withdrawn through line 10 responsive to slide valve 11. The. coolingof the briquettes can be accomplished by a wide variety of methods, suchas by the use of water quench in the form of mist, bedding them in coldfluid coke or by passing a gas such as cooled combustion gas over them.Vapors are withdrawn through line 12.

Referring now to Figure 2 heat treating vessel 102 is a multistageelongated vertical vessel. Vessel 102 consists of a tower containing aplurality of bubble plates or other gas pervious materials which permitbuild up of the fluid coke in the form of dense, turbulent, fluidizedbeds. Downcomers 104 are used but they have no weirs which would trapthe briquettes on the trays. The hub-- ble plates 103 preferably can besloped slightly from the horizontal, e. g. 1 to 4 to permit easier flowof the compactions. Air slides can be used at this point. Thecompactions enter an upper portion of the treating vessel through line101. They build up during the course of their downward flow through theheat treating vessel into a series of shallow moving beds of one or twolayers thick on each of the plates 103. They flow from the uppermoststages to the next lower stage, etc. The bed temperature can be1000-1800 F. at the bottom, e. g. 1200 F., and 200-800 F., e. g. 600 F.at the top, controlled by circulation rate to heater. Hot solids can beadded to the intermediate beds to flatten the temperature gradient. Thefluid coke at a temperature of 1500 F. is sent through line 109 to alower portion of treating vessel 102 and is built up into a series ofdense, turbulent beds on the plates 103 and is in countercurrent flow tothe compactions. The fines flow through the perforated plates. Theshallow beds of the compactions are thus contained in the fluid beds ofthe coke particles. Fluidizing gas to give a velocity of .1 to 3ft./sec., e. g. .5 ft./sec. enters through line 106. Exit gasesincluding fluidizing gas and evolved volatiles such as Hz, CH4, and H20are vented through cyclone 110 and line 111 with solid particles beingreturned through dipleg 112. Fluid coke is withdrawn from an upperportion of the vessel through line 107 and sent to heater 108 wherein itis reheated as discussed for Figure 1. Hot coke particles can beinjected into various points of the vessel 102 for selective purposessuch as to regulate temperature gradient. Time in the beds should besuch as to give the required drying and baking, so that the briquettesare sufliciently hardened before passing to the lower zones. The heathardened coke compactions are withdrawn through line 113 and can bequenched as stated previously.

The fines also flow down through downcomers along with descendingcompactions. This fines circulation is held to a moderate value byhaving a relatively small downcomer and high tray pressure drop. Noweirs on downcomers, so compactions flow freely. The flow of fines upthrough compactions tends to lift them so they move easily. Fines ofhigh density can be used so that compactions will have more tendency tofloat, e. g. calcined fines can be employed.

Data demonstrate that heating briquettes in fluid coke consistently gavesuperior results from those obtained in other heating methods such asutilizing a rotary kiln or using hot flue gas. The countercurrentcontacting of the compactions with fluidized coke particles can also beapplied to rotary kiln operations.

The conditions usually encountered in a fluid coker for fuels are alsolisted below so as to further illustrate how the fluid coke wasprepared.

Conditions in fluid coker reactor The advantages of this invention willbe apparent to the skilled in the art. Strong compactions are producedby heat hardening in a manner which prevents normal deformation. Inaddition a reducing atmosphere is made available during this heathardening treatment which prevents the excessive oxidation andconsequent weakening and yield degradation of the compactions.

It is tb be understood that this invention is not limited to thespecific examples which have been offered merely as illustrations andthat modifications may be made without departing from the spirit of theinvention.

What is claimed is:

1. In the heat hardening of compactlons of fluid coke with anagglutinating carbonaceous binder substance at heat hardeningtemperatures at which temperatures the compactions normally tend todeform and oxidize, the improvement which comprises the steps ofcountercurrently contacting the fluid coke compactions flowingdownwardly in the form of a moving bed with fluidized finer cokeparticles at heat hardening temperature in a vertical elongated heattreating zone, the compactions being fed to an upper portion of thetreating zone; withdrawing a portion of the coke particles from an upperportion of the treating zone; circulating them through an extraneousheating zone wherein their temperatures are elevated; returning them toa lower portion of the treating zone to supply heat thereto andwithdrawing the heat hardened compactions from the lower portion of thetreating zone.

2. The process of claim 1 in which the coke particles are in the form ofa dense, turbulent, fluidized bed.

3. The process of claim 2 in which the heat hardening temperature is inthe range of 1000" to 1800 F., the treating time is in the range of 15minutes to 2 hours, and the compactions treated contain about 5 to 20weight percent binder based on the fluid coke.

4. The process of claim 2 in which the coke particles in the dense,turbulent, fluidized bed are fluid coke particles.

5. The process of claim 4 in which the compactions being treated arebriquettes prepared by molding fluid coke with the binder underpressure.

6. In the heat hardening of compactions of fluid coke with anagglutinating carbonaceous binder substance at heat hardeningtemperatures at which temperatures the compactions normally tend todeform and oxidize, the improvement which comprises the steps of feedingthe fluid coke compactions to an upper portion of an elongated verticaltreating zone; passing the compactions downwardly through the treatingzone wherein they are treated counter-currently at heat hardeningtemperature in a plurality of superposed, shallow beds contained indense, turbulent fluidized beds of finer coke particles; withdrawing aportion of the coke particles from an upper portion of the treatingzone; circulating them through an extraneous heating zone wherein theirtemperatures are elevated; returning them to the lower portion of thetreating zone to supply heat'thereto and withdrawing the compactionsfrom the lower portion of the treating zone.

References Cited in the file of this patent UNITED STATES PATENTS2,556,154 Kern June 5, 1951 2,588,075 Barr et a1 Mar. 4, 1952 2,725,348Martin et al. Nov. 29, 1955 FOREIGN PATENTS 503,199 Belgium May 31, 1951

1. IN THE HEAT HARDENING OF COMPACTIONS OF FLUID COKE WITH ANAGGLUTINATING CARBONACEOUS BINDER SUBSTANCE AT HEAT HARDENINGTEMPERATURES AT WHICH TEMPERATURES THE COMPACTIONS NORMALLY TEND TODEFORM AND OXIDIZE, THE IMPROVEMENT WHICH COMPRISES THE STEPS OFCOUNTERCURRENTLY CONTACTING THE FLUID COKE CIMPACTIONS FLOWINGDOWNWARDLY IN THE FORM OF A MOVING BED WITH FLUIDIZED FINER COKEPARTICLES AT HEAT HARDENING TEMPERATURE IN A VERTICAL ELONGATED HEATTREATING ZONE, THE COMPACTIONS BEING FRED TO AN UPPER PORTION OF THETREATING ZONE; WITHDRAWING A PORTION OF THE COKE PARTICLES FROM AN UPPERPORTION OF THE TREATING ZONE; CIRCULATING THEM THROUGH AN EXTRANEOUSHEATING ZONE WHEREIN THEIR TEMPERATURES ARE ELEVATED; RETURNING THEM TOA LOWER PORTION OF THE TREATING ZONE TO SUPPLY HEAT THERETO ANDWITHDRAWING THE HEAT HARDENED COMPACTIONS FROM THE LOWER PORTION OF THETREATING ZONE.